I have created a guide on my user page that describes in detail how to use ScanTailor to process scanned images and prepare a PDF for uploading. It is bookended with instructions specific to scans from the New York Philharmonic archives, but the procedure can be adapted to any scan source. I used this method to prepare the Sinfonia Drammatica parts. If you find it useful or have any suggestions, please let me know, because it is still a work in progress!